1. Field Of The Invention
The present invention relates to audio-visual devices of the type adapted for use with an audio-visual unit, wherein the latter includes a holder mounting a plurality of discrete image transparencies arranged in a continuous pattern for successive visual display and an associated record including separate recorded messages corresponding to respective transparencies on the holder. More particularly, the present invention relates to an automatic reset mechanism for locating the tone arm in a position corresponding to the beginning groove of a selected one of such messages in response to certain movement of the mechanism which is employed for advancing the transparency holder to present the transparencies thereon in seriatim for visual display.
2. The Prior Art
Audio-visual devices of the type under consideration are known in the prior art. In this regard, reference is made to U.S. Pat. No. 3,685,892, issued to Alan G. Lewis, and assigned to the assignee of the present invention. The device shown in the Lewis patent is in the form of an audio-viewer adapted to receive an audio-visual unit consisting of a circular transparency holder and a record co-axially mounted on the holder for rotation relative thereto. This transparency holder mounts a circular or continuous pattern of transparency pairs for stereoscopic viewing. The record includes separate recorded messages corresponding to respective transparency pairs on the circular holder or disc.
The audio-viewing device according to the aforementioned patent contains a slot for removably receiving an audio-visual unit of the type just described. A manually operable advancing mechanism is provided for intermittently rotating the transparency holder to present the transparency pairs in seriatim for stereoscopic viewing. An indexing mechanism is operated in response to this actuation of the advancing mechanism for intermittently moving the tone arm to successive positions corresponding to the starting grooves of respective messages on the record.
The viewer disclosed in the Lewis patent includes automatic reset mechanism for the tone arm, which mechanism is operated by a lug or projection formed on the transparency disc. After the last pair of transparencies have been viewed, this lug actuates a tripping mechanism within the audio-visual device for automatically positioning the tone arm to the beginning groove of the first message on the record. Thus, according to the mechanism shown in this patent, the transparency pairs may be continuously and repeatedly viewed and at all times in synchronization with the recorded messages.
Although the reset mechanism in the Lewis patent is generally satisfactory, it suffers from two disadvantages. One of the disadvantages results from the requirement of forming the projection or lug on the transparency holder or disc -- it will be recalled from the foregoing description that such lug is necessary to actuate the tripping mechanism. This requirement complicates, to some degree, construction of the audio-visual unit which includes such transparency holder. Moreover, this requirement necessitates that the operator of the audio-viewer according to the Lewis patent must use the particular audio-visual unit described, i.e., a transparency holder with the projection or lug, to actuate the tripping mechanism and thus to enjoy the use of the automatic reset mechanism.
Another disadvantage flowing from the aforementioned Lewis construction resides in the fact that the operator must actuate a separate reset button or actuator to locate the tone arm in its proper position at the beginning of the audio-visual presentation. As more fully described in the Lewis patent, the operator must perform this step in order to establish initial synchronization between the beginning or starting transparency pair and the corresponding beginning audio message on the associated record.